Trifluridine–tipiracil plus bevacizumab versus trifluridine–tipiracil monotherapy for chemorefractory metastatic colorectal cancer: a systematic review and meta-analysis

Colorectal cancer is the leading cause of cancer death worldwide. The first and second lines of treatment for metastatic colorectal cancer (mCRC) include chemotherapy based on 5-fluorouracil. However, treatment following progression on the first and second line is still unclear. We searched PubMed, Scopus, Cochrane, and Web of Science databases for studies investigating the use of trifluridine-tipiracil with bevacizumab versus trifluridine-tipiracil alone for mCRC. We used RStudio version 4.2.3; and we considered p < 0.05 significant. Seven studies and 1,182 patients were included − 602 (51%) received trifluridine-tipiracil plus bevacizumab. Compared with control, the progression-free survival (PFS) (HR 0.52; 95% CI 0.42–0.63; p < 0.001) and overall survival (OS) (HR 0.61; 95% CI 0.52–0.70; p < 0.001) were significantly higher with bevacizumab. The objective response rate (ORR) (RR 3.14; 95% CI 1.51–6.51; p = 0.002) and disease control rate (DCR) (RR 1.66; 95% CI 1.28–2.16; p = 0.0001) favored the intervention. Regarding adverse events, the intervention had a higher rate of neutropenia (RR 1.38; 95% CI 1.19–1.59; p = 0.00001), whereas the monotherapy group had a higher risk of anemia (RR 0.60; 95% CI 0.44–0.82; p = 0.001). Our results support that the addition of bevacizumab is associated with a significant benefit in PFS, OS, ORR and DCR. Graphical Abstract Supplementary Information The online version contains supplementary material available at 10.1186/s12885-024-12447-8.


Introduction
Colorectal cancer (CRC) is one of the leading causes of cancer death, accounting for one in 10 cases, with an estimated 1,9 million new cases per year worldwide [1,2].Generally, first-and second-line treatment consists of fluorouracil-based chemotherapy with oxaliplatin and irinotecan, therapy targeting the vascular endothelial growth factor (VEGF) (mainly with Bevacizumab) or the epidermal growth factor receptor (EGFR) (the latter mainly in RAS wild-type tumors) [3][4][5][6].When disease progression occurs after these therapies, patients are considered chemorefractory; however, as many of these patients perform well for treatment, they may be eligible for additional therapies, as progression-free survival is less than 2 months without additional therapy [7][8][9][10].
Trifluridine/tipiracil is an orally administered combination of trifluridine, a nucleic acid analog, and tipiracil, a thymidine phosphorylase inhibitor [11,12].Trifluridine is an active cytotoxic component that, inside neoplastic cells, is phosphorylated by thymidine kinase to form trifluridine triphosphate, which acts by incorporating itself into the cell DNA in place of thymine [13].Thymidine phosphorylase is the enzyme responsible for the metabolism of trifluridine in the liver and gastrointestinal tract, transforming it into inactive forms; however, the addition of tipiracil to the combination is responsible for the total inhibition of this degradation, thus increasing the bioavailability of trifluridine [14,15].
Continuous inhibition of angiogenesis, particularly with anti-VEGF antibodies, is an effective strategy for treating metastatic CRC [16,17].Bevacizumab, an anti-VEGF antibody, improved progression-free survival and overall survival in patients with metastatic CRC when added to first-or second-line chemotherapy [18].More interestingly, the phase I/II C-TASK FORCE [19] study showed promising anti-tumor activity of TAS-102 (trifluridine/tipiracil) with bevacizumab in 25 colorectal cancer patients refractory to standard therapy.In this study, the median progression-free survival (PFS) was 5.6 months (95% CI; 3.4-7.6)and the median overall survival was 5.6 months (95% CI; 7.6-13.9).In contrast, these data are promising compared with those of large randomized trials that evaluated TAS-102 in monotherapy [20][21][22][23].
Thus, this meta-analysis clarified the real benefit of adding bevacizumab to trifluridine/tipiracil when compared directly with trifluridine/tipiracil in patients with chemorefractory metastatic CRC.

Protocol and registration
This systematic review adhered rigorously to the guidelines established by the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (Supplementary Tables 1  and 2) [24,25].To ensure transparency and reduce the risk of bias, the protocol was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO) under the registration number CRD42024498571.
The studies were selected on the basis of the PICOT question, including studies in patients with chemorefractory metastatic colorectal cancer (P-population) taking bevacizumab plus trifluridine/tipiracil (I-intervention) or trifluridine/tipiracil monotherapy (C-control) to evaluate efficacy and safety (O-outcome).Thus, we sought to answer the following question: the addition of bevacizumab to trifluridine/tipiracil is effective and safe?

Eligibility criteria
Studies that met the following eligibility criteria were included: (1) clinical case-control and cohort studies; (2) trifluridine/tipiracil (35 mg/m² of body surface area) orally twice a day on days 1-5 and 8-12 in a 28-day cycle with or without bevacizumab (5 mg/kg of body weight) administered by intravenous infusion every 2 weeks; (3) patients ≥ 18 years of age with metastatic colorectal cancer; (4) refractory to fluoropyrimidine, irinotecan, and oxaliplatin; and (5) patients who have progressed to at least 1 line of treatment.We excluded studies with overlapping populations, case reports, reviews, editorials, conference abstracts, and studies with no outcomes of interest.Inclusion and exclusion criteria for the studies included in the systematic review and meta-analysis are detailed in Table S3.

Search strategy
PubMed, Cochrane Library, Scopus, and Web of Science were systematically searched on December 17, 2023.
The detailed search strategy, utilizing MeSH terms, is provided in Table S4 of the Supplementary Material.To maximize capture of relevant studies, we went beyond the initial database search.Two reviewers (F.C.A.M. and F.D.D.L.P.) independently assessed the references of included articles and past systematic reviews.Additionally, we set up alerts in each database to automatically notify us of any newly published studies relevant to our inquiry.All identified articles, both from databases and reference lists, were imported into EndNote ® X7 (Thomson Reuters, Philadelphia, USA) for reference management.We employed a combined approach of automated and manual methods to meticulously remove duplicate entries.Subsequently, both reviewers independently screened the titles and abstracts of retrieved articles.Should any discrepancies arise, consensus was achieved through discussions involving the two reviewers and the senior author (N.P.C.S.).

Data extraction
The following baseline characteristics were extracted: (1) ClinicalTrials.govIdentifier; (1) study design; (3) regimen details in the intervention and control arm (Supplementary Table S5); (4) number of patients allocated for each arm; and (5) main patient characteristics.The ensuing outcomes of interest were extracted: (1) PFS, defined as the time from patient randomization to disease progression or death from any cause; (2) OS, defined as the time from the start of treatment that patients are still alive; (3) Disease control rate (DCR), defined as the sum of complete response (CR), partial response (PR) and stable disease (SD); (4) Objective response rate (ORR), defined as the sum of CR and PR [26]; and (5) adverse events, defined as an unwanted effect of a treatment, which were evaluated by the Common Terminology Criteria for Adverse Events, version 5.0 [27].Two authors (C.H.D.C.R. and F.D.D.L.P.) collected pre-specified baseline characteristics and outcome data.Where available, the full protocol of each study was consulted to verify study objectives, population, and other relevant information regarding study design and conduction.For publications reporting results from the same study, the most recent or complete publication reporting the information of interest was considered.

Risk of bias assessment
To ensure objectivity and minimize individual bias, three independent reviewers (F.D.D.L.P., C.H.D.C.R., and F.C.A.M.) evaluated the risk of bias within each included randomized controlled trial.Any discrepancies were resolved through consensus discussions to achieve a unified judgment.The Cochrane Collaboration tool for assessing risk of bias in randomized trials (RoB 2) was utilized for quality assessment of individual randomized studies [28].Each trial was assigned a score of high, low, or unclear risk of bias across five domains: randomization process, deviations from intended interventions, missing outcomes, measurement of outcomes, and selection of reported results.Non-randomized interventional studies were assessed through the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool [29], which contains seven domains and categorizes studies as having low, moderate, serious, critical, or unclear risk of bias.Funnel-plot analyses were employed to examine publication bias [30].

Statistical analysis
For time-to-event outcomes like progression-free survival (PFS) and overall survival (OS), we utilized the hazard ratio (HR) as the primary measure of effect.Higher HRs (> 1) favored the control group, indicating a greater risk of the event occurring in that group compared to the intervention group.Conversely, HRs less than 1 indicated a benefit associated with the intervention.For outcomes with binary endpoints, we employed risk ratios (RRs) alongside their corresponding 95% confidence intervals (CIs).These provided the relative risk of experiencing the event in one group compared to the other [31].The Sidik-Jonkman estimator was used to calculate the tau2 variance between studies [32].We used DerSimonian and Laird random-effect models for all endpoints [27].Publication bias was explored using Egger's linear regression test [33].The packages used were "meta" and "metagen".Statistical analyses were performed using R statistical software, version 4.2.3 (R Foundation for Statistical Computing).

Search results and characteristics of included studies
The selection process is shown in detail in a PRISMA flow diagram (Fig. 1).Our systematic search identified a total of 790 references.After removing 249 duplicates and screening titles and abstracts for eligibility, we excluded 477 references and assessed 64 full-text manuscripts for inclusion and exclusion criteria.Of these, seven studies [34][35][36][37][38][39][40] met the criteria and were included in the analysis: two clinical trials and five retrospective cohort studies.These seven studies comprised a total of 1,182 patients.

Discussion
In this systematic review and meta-analysis involving Our results showed that combining bevacizumab with trifluridine-tipiracil significantly improved PFS compared with trifluridine-tipiracil monotherapy (HR 0.52; 95% CI 0.42-0.63;p < 0.001).These results are encouraging, particularly when compared with other gastrointestinal cancers treated with anti-angiogenic agents.The study conducted by Okunaka et al. [41] showed that the addition of ramucirumab (VEGF inhibitor) to trifluridinetipiracil versus trifluridine-tipiracil monotherapy does not show a benefit for the PFS of patients with advanced gastric cancer (HR 0.66; 95% CI 0.43-1.03;p = 0.059).
In addition, bevacizumab therapy had a higher absolute DCR (RR 1.66; 95% CI 1.28-2.16;p = 0.0001).This association signals promising prospects for metastatic colorectal cancer, where the addition of new emerging therapies does not always result in an additive benefit.Thus, contrary to our results, the meta-analysis conducted by Zeng et al. [45] showed that the use of immunotherapy, particularly immune checkpoint inhibitors, in colorectal cancer does not seem to be associated with any benefit for DCR (OR 0.97; 95% CI 0.36-2.61;p = 0.95).
Adverse events associated with cancer treatment affect the physical and emotional well-being and quality of life and can compromise the activities of daily living of patients with colorectal cancer [46].Although the incidence of adverse events is higher for most combination chemotherapies, only neutropenia was associated with the addition of bevacizumab (p = 0.00001); more interestingly, trifluridine-tipiracil monotherapy seems to have increased anemia in severe grades (p = 0.001), suggesting that bevacizumab could be protective for this adverse event.
This study has some limitations.First, the analysis was mainly based on observational and non-randomized studies, which may have influenced the effect size found in our results.However, the absence of heterogeneity in the pooled analysis of most of the results suggests that our meta-analysis conveys the best available evidence.Second, the studies had different patient follow-up times, which may have affected our results.However, despite the limitations presented, this did not prevent robust conclusions on efficacy and safety outcomes showing the potential benefit of bevacizumab combined with trifluridine-tipiracil.

Conclusion
This is the first meta-analysis to evaluate trifluridinetipiracil plus bevacizumab versus trifluridine-tipiracil monotherapy for chemorefractory metastatic colorectal cancer.Our results support the notion that the addition of bevacizumab to trifluridine-tipiracil is associated with a significant improvement in PFS, OS, ORR, and DCR, suggesting the antitumor potential of this combination therapy.

Fig. 1
Fig. 1 PRISMA flow diagram of study screening and selection

7 studies and 1 ,
182 patients, we compared Trifluridine-Tipiracil plus Bevacizumab versus Trifluridine-Tipiracil Monotherapy in patients with metastatic colorectal cancer.The main results of the pooled analyses were as follows: (1) PFS was better in patients receiving trifluridine-tipiracil plus bevacizumab; (2) OS showed a significant difference in favor of the trifluridine-tipiracil plus bevacizumab group; (3) Clinical responses to treatment, such as ORR and DCR, were significantly beneficial in the bevacizumab group; and (3) adverse effects such as neutropenia and anemia were observed in both treatment groups.

Table 1
Baseline characteristics of included studies RCT Randomized Controlled Trial, RCS Retrospective Cohort Study, I Intervention group, C Control group, PS-ECOG Performance Status of Eastern Cooperative Oncology Group, RS Right side, LS Left side, No Number, CI

Table 2
Statistical analysis of the adverse events RR Risk ratio, CI Confidence interval, No Number 4ig.4Funnel plot analysis of the disease control rate of patients with metastatic colorectal cancer